The present invention relates to a gas turbine intake air cooling apparatus for cooling gas turbine intake air with fuel for driving the gas turbine such as liquified natural gas (hereunder, referred to as LNG) and to a method of operation of the apparatus.
Recently, combined power plants using gas turbines have increased in ratio of power supply as compared with conventional steam power plants because the former is higher in efficiency than the latter.
Gas turbines each have a construction that a lot of air is taken by a rotary compressor and its output is generated by expanding the air, so that the specific gravity of the air influences greatly on the output. The higher the temperature of the atmosphere becomes, the smaller the specific gravity thereof becomes, and the gas turbine has a characteristic that its output decreases thereof decrease as well. On the other hand, since the peak of electric power demand is in summer, more power is required in summer when the atmosphere temperature is high. This is contrary to the characteristic of the gas turbine. It is necessary to effectively supply electric power without decreasing power generation of the gas turbine even if the atmosphere temperature is high.
According to such a demand, a gas turbine intake air cooling method is proposed, wherein decrease in gas turbine output in summer is prevented by lowering the gas turbine intake air temperature below atmosphere temperature and supplying the intake air lowered in temperature. Japanese Utility-Model Publication No. 61-37794 discloses a method in which LNG cold energy lowers temperature of brine as a heat medium, the brine is brought into direct contact with gas turbine intake air to lower the temperature thereof. Japanese Patent Laid-open Application No. 1-142219 discloses a method in which LNG cold energy lowers a temperature of a heat medium and the heat medium lowered in temperature cools directly gas turbine intake air or indirectly cools the gas turbine intake air using a heat medium. In the laid-open application, water or a mixture of ethylene glycol and water may be used as those heat mediums.
In the above former method using the brine as a heat medium directly in contact with LNG cold energy, the brine is easily frozen because of a temperature difference between a boiling temperature -162.degree. C. of LNG and a solidifying point -22.degree. C. of the brine, which is a bar to recirculation of the brine. The above latter method also has a problem similar to the former method.
Further, since the peak of power demand is in summer, particularly in the daytime of summer, it is desirable to cool gas turbine intake air by using cold energy of a heat accumulator in the daytime thereby to effect heat dissipation operation of the heat accumulator for increasing output of the gas turbine and to effect heat accumulation of LNG cold energy at night because cold for cooling the gas turbine intake air is unnecessary or smaller than in the daytime. However, it is difficult for conventional heat accumulators to carry out a lot of heat dissipation and heat accumulation at the same time because of insufficient capacity of the heat accumulators.